Ruins of the 13th century Kalo castle can be found in Mols Bjerge National Park in Denmark. The castle was built by a Danish king Erik Menved and later maintained by the county men till 1660. The castle is now a popular tourist attraction consisting of a main central tower and some recreational areas around the northern peninsula. Climb the castle tower staircase to get unobstructed views of the ruins, the salt marshes and the endless blue sea. During summer holidays, free guided tours of the area are open for children.